Free cutting alloy

Abstract

Provided is free cutting alloy excellent in machinability, preserving various characteristics as alloy. The free cutting alloy contains: one or more of Ti and Zr as a metal element component; and C being an indispensable element as a bonding component with the metal element component, wherein a (Ti,Zr) based compound including one or more of S, Se and Te is formed in a matrix metal phase. The free cutting alloy is more excellent in machinability, preserving various characteristics as alloy at similar levels to a conventional case. The effect is especially conspicuous, for example, when a compound expressed in a chemical form of (Ti,Zr) 4 C 2 (S,Se,Te) 2 as the (Ti,Zr) based compound is formed at least in a dispersed state in the alloy structure.

What is claimed is: 
     
       1. Free cutting alloy constituted as ferrite containing stainless steel containing:
 2 mass % or lower, including zero, Ni; 12 to 35 mass % Cr; and 0.021 to 0.4 mass % C; 
 one or more of Ti and Zr such that W Ti +0.52W Zr =0.14 to 3.5 mass %, wherein W Ti  and W Zr  denote respective contents in mass % of Ti and Zr; and one or more of S and Se in the respective ranges of 0.01 to 1 mass % for S and 0.01 to 0.8 mass % for Se so that a total content in mass % of S and Se is set to a value higher than two times a C content in mass %; 
 wherein S content is determined such that a value of W S /(W Ti +0.52W Zr ) is 0.45 or less, wherein W S  denotes a S content; 
 wherein (W Ti +0.52W Zr )/W c =6.7 to 20, wherein W c  donates content in mass % of C; 
 and wherein a (Ti,Zr) based compound containing one or more of Ti and Zr as a metal element component, C being an indispensable element as a bonding component with the metal element component, and one or more of S, Se and Te is dispersed in a matrix metal phase. 
 
     
     
       2. Free cutting alloy according to  claim 1 , the W so  value of which is less than 0.035 mass % when the following test is performed: an alloy test piece is prepared so as to have the shape of a rectangular prism in size of 15 mm in length, 25 mm in width and 3 mm in thickness with the entire surface being polished with No. 400 emery paper; a silver foil in size of 10 mm in length, 5 mm in width and 0.1 mm in thickness with a purity of 99.9% or higher as a S getter and 0.5 cc of pure water are sealed in a vessel of an inner volume of 250 cc together with said test piece; a temperature in said vessel is raised to 85° C. and said temperature is then kept there for 20 hr; and thereafter, a S content W SO  in mass % in said silver foil piece is analyzed. 
     
     
       3. Free cutting alloy according to  claim 1 , containing 2 mass % or lower Si; 2 mass % or lower Mn; 2 mass % or lower Cu; and 2 mass % or lower Co. 
     
     
       4. Free cutting alloy according to  claim 1 , containing one or more of Mo and W in the respective ranges of 0.1 to 4 mass % for Mo and 0.1 to 3 mass % for W. 
     
     
       5. Free cutting alloy according to  claim 1 , containing: 0.05 mass % or lower P; and 0.03 mass % O; and 0.05 mass % or lower N. 
     
     
       6. Free cutting alloy according to  claim 1 , containing one or more of Te, Bi and Pb in the respective ranges of 0.005 to 0.1 mass % for Te; 0.01 to 0.2 mass % for Bi; and 0.01 to 0.3 mass % for Pb. 
     
     
       7. Free cutting alloy according to  claim 1 , containing one or more selected from the group consisting of Ca, Mg, B and metal elements classified as Group 3A in the periodic table of elements in the range of 0.0005 to 0.01 mass % for one element or as a total content of more than one elements combined. 
     
     
       8. Free cutting alloy according to  claim 1 , containing one or more selected from the group consisting of Nb, V, Ta and Hf each of which is in a range of 0.01 to 0.5 mass %. 
     
     
       9. Free cutting alloy constituted as martensite containing stainless steel containing:
 2 mass % or lower, including zero, Ni; 9 to 17 mass % Cr; 0.03 mass % or lower O; 0.05 mass % or lower N; 
 one or more of Ti and Zr such that W Ti +0.52W Zr =0.10 to 3.5 mass %, wherein W Ti  and W Zr  denote respective contents in mass % of Ti and Zr; and one or more of S and Se in the respective ranges of 0.03 to 1 mass % for S and 0.01 to 0.8 mass % for Se; 
 and 0.19 mass % or more of C so as to satisfy the following formulae:
   0.375( W   S +0.4 W   Se )< W   C ≦1.5   (Formula A)
 
   0.125( W   Ti +0.52 W   Zr )< W   C ≦1.5   (Formula B),
 
 
 wherein W Ti , W Zr  W C , W S  and W Se  denote respective contents of Ti, Zr, C, S and Se, all in mass %; 
 and wherein a (Ti,Zr) based compound containing one or more of Ti and Zr as a metal element component, C being an indispensable element as a bonding component with the metal element component, and one or more of S, Se and Te is dispersed in a matrix metal phase. 
 
     
     
       10. Free cutting alloy according to  claim 9  whose S content is determined such that a value of W S /(W Ti +0.52W Zr ) is 0.45 or less, wherein W S  denotes a S content. 
     
     
       11. Free cutting alloy according to  claim 10 , the W so  value of which is less than 0.035 mass % when the following test is performed: an alloy test piece is prepared so as to have the shape of a rectangular prism in size of 15 mm in length, 25 mm in width and 3 mm in thickness with the entire surface being polished with No. 400 emery paper; a silver foil in size of 10 mm in length, 5 mm in width and 0.1 mm in thickness with a purity of 99.9% or higher as a S getter and 0.5 cc of pure water are sealed in a vessel of an inner volume of 250 cc together with said test piece; a temperature in said vessel is raised to 85° C. and said temperature is then kept there for 20 hr; and thereafter, a S content W SO  in mass % in said silver foil piece is analyzed. 
     
     
       12. Free cutting alloy according to  claim 9  further containing: 2 mass % or lower Si; 2 mass % or lower Mn; 2 mass % or lower Cu; and 2 mass % or lower Co. 
     
     
       13. Free cutting alloy according to  claim 9  further containing one or more of Mo and W in the respective ranges of 0.1 to 4 mass % for Mo and 0.1 to 3 mass % for W. 
     
     
       14. Free cutting alloy according to  claim 9  further containing: 0.05 mass % or lower P; and 0.03 mass % or lower O; and 0.05 mass % or lower N. 
     
     
       15. Free cutting alloy according to  claim 9  further containing one or more of Te, Bi and Pb in the respective ranges of 0.005 to 0.1 mass % for Te; 0.01 to 0.2 mass % for Bi; and 0.01 to 0.3 mass % for Pb. 
     
     
       16. Free cutting alloy according to  claim 9  further containing one or more selected from the group consisting of Ca, Mg, B and metal elements classified as Group 3A in the periodic table of elements in the range of 0.0005 to 0.01 mass % for one element or as a total content of more than one elements combined. 
     
     
       17. Free cutting alloy according to  claim 9  further containing one or more selected from the group consisting of Nb, V, Ta and Hf each of which is in a range of 0.01 to 0.5 mass %. 
     
     
       18. Free cutting alloy containing 20 to 82 mass % Ni and the part except for Ni of which is mainly constituted by one or more of Fe and Cr further containing:
 one or more of Ti and Zr so that X defined by the following formula 1 in the range satisfying a relation of 0.05≦X≦3; 
 one or more of S, Se and Te so that Y defined by the following formula 2 in the range satisfying a relation of 0.014≦Y≦0.5 X; 
 C in the range satisfying a relation of 0.2Y≦W C ≦0.3, wherein when a Ti content is indicated by W Ti  in mass %, a Zr content by W Zr  in mass %, a C content by W C  in mass %, a S content by W S  in mass %, a Se content by W Se  in mass % and a Te content by W Te  in mass %, the following formulae 1 and 2 are given in order to define X and Y:
     X (mass %)= W   Ti +0.52 W   Zr    (formula 1)
 
     Y (mass %)= W   S +0.41 W   Se +0.25 W   Te    (formula 2);
 
 
 one or more of Si, Mn and Al in the respective ranges of 1 mass % for Si, 1 mass % for Mn and 1 mass % for Al; 
 wherein a (Ti,Zr) based compound containing one or more of Ti and Zr as a metal element component, C being an indispensable element as a bonding component with the metal element component, and one or more of S, Se and Te is dispersed in a matrix metal phase. 
 
     
     
       19. Free cutting alloy according to  claim 18  further containing one or more of Mo and Cu in the respective ranges of 7 mass % or lower for Mo and 7 mass % or lower for Cu. 
     
     
       20. Free cutting alloy according to  claim 18  further containing 12 mass % or lower Cr. 
     
     
       21. Free cutting alloy according to  claim 18  further containing 18 mass % or lower Co.